I got hold of a au W65S Xmini cellphone pretty cheap, and am selling it online at Yahoo Auction in Japan. It's made by Sony Ericsson. The device is a Walkman cellphone, so the sound quality should be good. (I don't have a valid IC card to test this at the moment)

The device is very small, so I guess it's easy to lose it, but it's really good for those who just love tiny cell phones.